Role of Background Meridional Moisture Gradient (MMG) on the Propagation of the MJO Over the Maritime Continent
The Madden-Julian Oscillation (MJO) exhibits considerable year-to-year variability. Motivated by the recent studies that highlighted the role of the background moisture gradient on the propagation of the MJO, this study examined the influence of the background meridional moisture gradient (MMG) on MJO propagation at the interannual timescale during boreal winter.
Our results demonstrate that the interannual variability of the seasonal mean MMG over the southern Maritime Continent (MC) area is associated with the meridional expansion and contraction of the moist area in the vicinity of the MC, and it has strong control over the propagation characteristics of the MJO in the MC region.
This study investigates the role of the background meridional moisture gradient (MMG) on the propagation of the Madden–Julian Oscillation (MJO) across the Maritime Continent (MC) region. By contrasting the years with anomalously low and high MMG, we show that MJO propagation through the MC is enhanced (suppressed) in years with higher (lower) seasonal mean MMG, though the effect is less robust when MMG anomalies are weak. Column-integrated moisture budget analysis further shows that sufficiently large MMG anomalies affect MJO activity by modulating the meridional advection of the mean moisture via MJO wind anomalies.